Apex domains cannot have CNAME records.
Question and response
Question
dig ns.visp.net. NS
Answer
ns.visp.net. 5 NS ns2.visp.net.
ns.visp.net. 5 NS ns.visp.net.
Authority
The response has no authority records.
Additional
ns.visp.net. 5 A 54.68.129.253
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0